Sorting Strings that contains number in kotlin

Question

I wanna sort some strings that contain numbers but after a sort, it becomes like this ["s1", "s10", "s11", ... ,"s2", "s21", "s22"]. after i search i fount this question with same problem. but in my example, I have mutableList<myModel>, and I must put all string in myModel.title for example into a mutable list and place into under code:

   val sortData = reversedData.sortedBy {
          //pattern.matcher(it.title).matches()
             Collections.sort(it.title, object : Comparator<String> {
                override fun compare(o1: String, o2: String): Int {
                    return extractInt(o1) - extractInt(o2)
                }

                 fun extractInt(s: String): Int {
                     val num = s.replace("\\D".toRegex(), "")
                     // return 0 if no digits found
                     return if (num.isEmpty()) 0 else Integer.parseInt(num)
                 }
            })
        }

I have an error in .sortedBy and Collections.sort(it.title), may please help me to fix this.

at first, I must find a way to convert it.title to mutable list. because Collections.sort need that. I don't know how to push all it.title from a model into a mutable list and then I think I must use return before Collections.sort for fixing .sortedBy — Mehrdad Dolatkhah
– Mehrdad Dolatkhah, Commented Dec 10, 2018 at 11:59
don't mix Collections.sort and sortedBy. You may want to have a look at sortWith instead.... also: sortedBy and sortedWith are similar (they return a new list), whereas sortWith operates on the current list... — Roland
– Roland, Commented Dec 10, 2018 at 12:32
how can the accepted answer be the answer to your problem? it is way too complicated than any other answer, it uses Observable/Subscriber, something you didn't... — Roland
– Roland, Commented Dec 11, 2018 at 15:19

hakim · Accepted Answer · 2018-12-10 12:53:05Z

9

you can use sortWith instead of sortBy for example:

class Test(val title:String) {
  override fun toString(): String {
    return "$title"
  }
}

val list = listOf<Test>(Test("s1"), Test("s101"),
Test("s131"), Test("s321"), Test("s23"), Test("s21"), Test("s22"))
val sortData = list.sortedWith( object : Comparator<Test> {
override fun compare(o1: Test, o2: Test): Int {
    return extractInt(o1) - extractInt(o2)
}

fun extractInt(s: Test): Int {
    val num = s.title.replace("\\D".toRegex(), "")
    // return 0 if no digits found
    return if (num.isEmpty()) 0 else Integer.parseInt(num)
}

})

will give output: [s1, s21, s22, s23, s101, s131, s321]

edited Dec 10, 2018 at 12:53

answered Dec 10, 2018 at 11:56

hakim

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2 Comments

Mehrdad Dolatkhah Over a year ago

how I must push all it.title into a list and use in sortData ?

hakim Over a year ago

@MehrdadDolatkhah I update my sample, hopefully it can give you the idea how to solve your problem, how to access title (attribute). change class Test with your MyModel class

m0skit0 · Accepted Answer · 2018-12-10 11:55:57Z

5

A possible solution based on the data you posted:

sortedBy { "s(\\d+)".toRegex().matchEntire(it)?.groups?.get(1)?.value?.toInt() }

Of course I would move the regex out of the lambda, but it is a more concise answer this way.

answered Dec 10, 2018 at 11:55

m0skit0

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Comments

alireza davari · Accepted Answer · 2018-12-11 05:50:52Z

2

A possible solution can be this:

  reversedData.toObservable()
                    .sorted { o1, o2 ->
                        val pattern = Pattern.compile("\\d+")
                        val matcher = pattern.matcher(o1.title)
                        val matcher2 = pattern.matcher(o2.title)

                        if (matcher.find()) {
                            matcher2.find()
                            val o1Num = matcher.group(0).toInt()
                            val o2Num = matcher2.group(0).toInt()

                            return@sorted o1Num - o2Num
                        } else {
                            return@sorted o1.title?.compareTo(o2.title ?: "") ?: 0
                        }
                    }
                    .toList()
                    .subscribeBy(
                        onError = {
                            it
                        },
                        onSuccess = {
                            reversedData = it
                        }
                    )

answered Dec 11, 2018 at 5:50

alireza davari

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1 Comment

m0skit0 Over a year ago

Use Kotlin's regex extensions, they're shorter and simpler. Check my answer for an example.

Roland · Accepted Answer · 2018-12-10 12:17:53Z

As you state that you need a MutableList, but don't have one yet, you should use sortedBy or sortedWith (in case you want to work with a comparator) instead and you get just a (new) list out of your current one, e.g.:

val yourMutableSortedList = reversedData.sortedBy {
  pattern.find(it)?.value?.toInt() ?: 0
}.toMutableList() // now calling toMutableList only because you said you require one... so why don't just sorting it into a new list and returning a mutable list afterwards?

You may want to take advantage of compareBy (or Javas Comparator.comparing) for sortedWith.

If you just want to sort an existing mutable list use sortWith (or Collections.sort):

reversedData.sortWith(compareBy {
  pattern.find(it)?.value?.toInt() ?: 0
})

// or using Java imports:
Collections.sort(reversedData, Compatarator.comparingInt {
  pattern.find(it)?.value?.toInt() ?: 0 // what would be the default for non-matching ones?
})

Of course you can also play around with other comparator helpers (e.g. mixing nulls last, or similar), e.g.:

reversedData.sortWith(nullsLast(compareBy {
  pattern.find(it)?.value
}))

For the samples above I used the following Regex:

val pattern = """\d+""".toRegex()

eriegz · Accepted Answer · 2023-12-06 18:04:26Z

None of the other answers on this page worked for me, or were too confusing, so I'm sharing my simpler solution that I came up with:

Short answer:

Simply call:

yourArray.sortedWith(::numberAwareAlphabeticalSort)

And what is numberAwareAlphabeticalSort, you ask? It's a simple function that you copy-paste somewhere into your code. See full answer below:

Long answer:

This example code below is fully copy-pasteable. Here's a link to a Kotlin REPL where you can try it out yourself: https://pl.kotl.in/oPGE-NekG

val unsortedList = listOf(
    "Zebra",
    "Title 1",
    "Title 10",
    "A title 2",
    "Title 3",
    "Aardvark",
)

// Our helper function which looks for numbers at the end of a string:
fun extractIntegerFromEndOfString(input: String): Int? {
    val words = input.split(" ")
    val lastWord = words.lastOrNull()

    return if (lastWord != null && lastWord.all { it.isDigit() }) {
        lastWord.toInt()
    } else {
        null
    }
}

// Our actual sorting function:
fun numberAwareAlphabeticalSort(item1: String, item2: String): Int {
    val number1 = extractIntegerFromEndOfString(item1)
    val number2 = extractIntegerFromEndOfString(item2)

    return if (number1 != null && number2 != null) {
        // Slice off the number from the end of both strings:
        //   - if the remaining portions of each string are identical, then compare the two integer values that
        //     you extracted
        //   - otherwise, simply compare the two remaining portions alphabetically
        val remaining1 = item1.substring(0, item1.length - number1.toString().length).trim()
        val remaining2 = item2.substring(0, item2.length - number2.toString().length).trim()

        if (remaining1 == remaining2) {
            number1.compareTo(number2)
        } else {
            remaining1.compareTo(remaining2)
        }
    } else {
        // Otherwise, one or both items don't have numbers at the end, so just compare them alphabetically:
        item1.compareTo(item2)
    }
}

val sortedIntelligently = unsortedList.sortedWith(::numberAwareAlphabeticalSort)

sortedIntelligently.map { println(it) }
// Outputs:
//
// A title 2
// Aardvark
// Title 1
// Title 3
// Title 10
// Zebra

Polv · Accepted Answer · 2019-04-11 04:53:01Z

-1

I wrote a custom comparator for my JSON sorting. It can be adapted from bare String/Number/Null

fun getComparator(sortBy: String, desc: Boolean = false): Comparator<SearchResource.SearchResult> {
    return Comparator { o1, o2 ->
        val v1 = getCompValue(o1, sortBy)
        val v2 = getCompValue(o2, sortBy)

        (if (v1 is Float && v2 is Float) {
            v1 - v2
        } else if (v1 is String && v2 is String) {
            v1.compareTo(v2).toFloat()
        } else {
            getCompDefault(v1) - getCompDefault(v2)
        }).sign.toInt() * (if (desc) -1 else 1)
    }
}

private fun getCompValue(o: SearchResource.SearchResult, sortBy: String): Any? {
    val sorter = gson.fromJson<JsonObject>(gson.toJson(o))[sortBy]
    try {
        return sorter.asFloat
    } catch (e: ClassCastException) {
        try {
            return sorter.asString
        } catch (e: ClassCastException) {
            return null
        }
    }
}

private fun getCompDefault(v: Any?): Float {
    return if (v is Float) v else if (v is String) Float.POSITIVE_INFINITY else Float.NEGATIVE_INFINITY
}

answered Apr 11, 2019 at 4:53

Polv

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1 Comment

UnknownUser Over a year ago

So adapt your comparator and share adapted version please.

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